Effects of ethanol, tannin and fructose on the sensory and chemical properties of Washington State Merlot

Anne Carolyn Secor

The relationship between matrix components and sensory properties of red wine was examined. A Washington State Merlot was dealcoholized to 3.2% and alcohol was added back to four ethanol levels: 3.2%, 8%, 12% and 16% ethanol (v/v). Within each treatment, wines were maintained at the original tannin (211 mg/L CE tannin) and fructose (120 mg/L fructose), or brought to 1500 mg/L CE tannin and/or 2000 mg/L fructose (n=16 solutions). The wines were spiked with the same concentrations of three aroma compounds: 3-methyl-1-butanol, 2- phenylethanol, and eugenol. These wines were then evaluated by a trained panel (n=10) for the intensity of aromas and flavors ('caramel', 'rose' and 'clove'), tastes ('bitterness' and 'sourness'), and mouthfeel ('astringency' and 'heat'). Gas chromatography/mass spectrometry was used to quantify aroma compounds. PCA was used for correlation between sensory and analytical results. All data were analyzed using analysis of variance (p<0.05) and Fisher's Least Significant Difference. Analytical results showed that ethanol significantly reduced the relative headspace recovery of all three compounds. The interaction effects between ethanol, tannin and fructose varied based upon the aroma compound and the ethanol content. In standard red wine ethanol concentrations (12 to 16%), volatile recovery was not influenced by tannin or fructose. However, in low ethanol wines, high tannin concentration negatively impacted the relative recovery of 3-methyl-1-butanol, 2-phenylethanol, and eugenol. An increase in fructose concentration when ethanol and tannin concentrations were low reduced the recovery of 3- methyl-1-butanol, but increased the recovery of 2-phenylethanol. The trained panel sensory evaluation results showed that increasing ethanol concentrations increased 'clove' flavor, and 'heat', and decreased 'sourness' intensity. High fructose concentration increased 'rose' aroma and flavor scores, and decreased 'clove' aroma scores. Tannin concentration positively affected 'clove' flavor while perceived 'drying' and 'bitterness' were impacted by ethanol*tannin. PCA separated treatments based on ethanol, tannin, and fructose concentrations, and chemical analyses of aroma compounds were not correlated with perceived aromas or flavors. This study demonstrated the complexity of relationships within the wine matrix, indicating chemical and sensory effects that winemaking techniques such as saigneé, the addition of water, and dealcoholization may have on wine quality.

Effects of ethanol, tannin and fructose on the sensory and chemical properties of Washington State Merlot

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